Cutting insert and cutting tool

Abstract

A cutting insert includes an insert body, a rake face on an upper surface of an end portion of the insert body, a cutting edge on a ridge between the rake face and an end surface of the insert body, side cutting edges on ridges between the rake face and side surfaces of the insert body, each connected to both end portions of the cutting edge, and a breaker convex portion on the rake face. The breaker convex portion includes two breaker island portions extending toward the side cutting edge as extending closer to the front cutting edge. Each breaker island portion includes from the front cutting edge side a first raised portion, a descending portion which becomes lower from a top portion of the first raised portion, and a second raised portion which becomes higher, from the descending portion, than the top portion of the first raised portion.

The invention claimed is: 
     
       1. A cutting insert, comprising:
 an insert body in a prism shape; 
 a rake face on an upper surface at an end portion of the insert body in a longitudinal direction; 
 a front cutting edge on a ridge line between the rake face and an end surface of the insert body; 
 side cutting edges on ridge lines between the rake face and side surfaces of the insert body, being respectively connected to the front cutting edge; and 
 a breaker convex portion on the rake face, 
 wherein the breaker convex portion includes two breaker island portions which extend toward the side cutting edge sides as extending closer to the front cutting edge side, each of the breaker island portions includes from the front cutting edge side a first raised portion, a descending portion which gradually becomes lower from a top portion of the first raised portion, and a second raised portion which gradually becomes higher, from the descending portion, than the top portion of the first raised portion, and 
 wherein, between the two breaker island portions, a breaker groove and a center raised portion are provided from the front cutting edge side, and both side ends of the center raised portion are respectively coupled to both rear end parts of the two breaker island portions furthest from the front cutting edge. 
 
     
     
       2. The cutting insert according to  claim 1 ,
 wherein a top portion of the second raised portion of the two breaker island portions is higher than a top portion of the center raised portion. 
 
     
     
       3. The cutting insert according to  claim 1 ,
 wherein, in side view, a rising angle of the first raised portion is larger than a rising angle of the second raised portion. 
 
     
     
       4. The cutting insert according to  claim 1 ,
 wherein the first raised portion, the descending portion, and the second raised portion include convex surfaces protruding to an upper side. 
 
     
     
       5. The cutting insert according to  claim 4 ,
 wherein, in plan view, when a line through the top of the convex surface of the first raised portion is a first ridge line, and a line through the top of the convex surface of the second raised portion is a second ridge line, the first ridge line and the second ridge line are provided to extend closer to a side end of the rake face as the breaker island portion extending toward the end surface side with respect to the longitudinal direction of the insert body. 
 
     
     
       6. The cutting insert according to  claim 5 ,
 wherein a shift angle of the second ridge line with respect to the longitudinal direction of the insert body is larger than a shift angle of the first ridge line with respect to the longitudinal direction of the insert body. 
 
     
     
       7. The cutting insert according to  claim 1 ,
 wherein, in plan view, a maximum width of the second raised portion is larger than a maximum width of the first raised portion. 
 
     
     
       8. The cutting insert according to  claim 1 ,
 wherein a preliminary raised portion is provided at a portion closer to the front cutting edge than the first raised portion, and a rising angle of the preliminary raised portion is smaller than the rising angle of the first raised portion. 
 
     
     
       9. The cutting insert according to  claim 1 ,
 wherein the two breaker island portions are line symmetrical with respect to a center line which passes through the center of the front cutting edge and is parallel to the longitudinal direction of the insert body. 
 
     
     
       10. A cutting tool, comprising:
 The cutting insert according to  claim 1 , and 
 a holder which includes an insert mounting space, 
 wherein the cutting insert is mounted in the insert mounting space of the holder such that the front cutting edge of the cutting insert is located outside the holder. 
 
     
     
       11. A cutting insert, comprising:
 an insert body in a prism shape; 
 a rake face on an upper surface at an end portion of the insert body in a longitudinal direction; 
 a front cutting edge on a ridge line between the rake face and an end surface of the insert body; 
 side cutting edges on ridge lines between the rake face and side surfaces of the insert body, being respectively connected to the front cutting edge; and 
 a breaker convex portion on the rake face, 
 wherein the breaker convex portion includes two breaker island portions which extend toward the side cutting edge sides as extending closer to the front cutting edge side, each of the breaker island portions includes from the front cutting edge side a first raised portion, a descending portion which gradually becomes lower from a top portion of the first raised portion, and a second raised portion which gradually becomes higher, from the descending portion, than the top portion of the first raised portion, 
 wherein, between the two breaker island portions, a breaker groove and a center raised portion are provided from the front cutting edge side, and both side ends of the center raised portion are respectively coupled to the two breaker island portions, and 
 wherein the center raised portion is located farther from the front cutting edge than the descending portion. 
 
     
     
       12. The cutting insert according to  claim 11 ,
 wherein a top portion of the second raised portion of the two breaker island portions is higher than a top portion of the center raised portion. 
 
     
     
       13. The cutting insert according to  claim 11 ,
 wherein, in side view, a rising angle of the first raised portion is larger than a rising angle of the second raised portion. 
 
     
     
       14. The cutting insert according to  claim 11 ,
 wherein the first raised portion, the descending portion, and the second raised portion include convex surfaces protruding to an upper side. 
 
     
     
       15. The cutting insert according to  claim 14 ,
 wherein, in plan view, when a line through the top of the convex surface of the first raised portion is a first ridge line, and a line through the top of the convex surface of the second raised portion is a second ridge line, the first ridge line and the second ridge line are provided to extend closer to a side end of the rake face as the breaker island portion extending toward the end surface side with respect to the longitudinal direction of the insert body. 
 
     
     
       16. The cutting insert according to  claim 15 ,
 wherein a shift angle of the second ridge line with respect to the longitudinal direction of the insert body is larger than a shift angle of the first ridge line with respect to the longitudinal direction of the insert body. 
 
     
     
       17. The cutting insert according to  claim 11 ,
 wherein, in plan view, a maximum width of the second raised portion is larger than a maximum width of the first raised portion. 
 
     
     
       18. The cutting insert according to  claim 11 ,
 wherein a preliminary raised portion is provided at a portion closer to the front cutting edge than the first raised portion, and a rising angle of the preliminary raised portion is smaller than the rising angle of the first raised portion. 
 
     
     
       19. The cutting insert according to  claim 11 ,
 wherein the two breaker island portions are line symmetrical with respect to a center line which passes through the center of the front cutting edge and is parallel to the longitudinal direction of the insert body.